Iraq’s president named prominent Shiite politician Haider al-Abadi as new prime minister and has asked him to form a new government. The move dislodges Nouri al-Maliki, who has been widely blamed for the growth of the Islamic State. (The Washington Post)

Iran endorsed Iraq’s prime minister designate on Tuesday, striking a decisive blow against incumbent Nouri al-Maliki as a wide spectrum of domestic factions — and even his most loyal militia — also turned their backs on the country’s longtime leader.

Maliki’s growing isolation raised hopes of a relatively smooth transfer of power after a tense two-day standoff during which the desperate incumbent deployed security forces to strategic points across the capital.

The Iranian leadership, which wields significant influence in Iraqi politics, joined a range of Iraqi political groups — including Kurds, Sunnis and Shiites — in backing Shiite politician Haider al-Abadi’s efforts to form a new government.

The United States and many Iraqis see the creation of a new, more inclusive government as crucial to peeling away support for the Sunni extremists of the Islamic State. Maliki, a Shiite, had marginalized the country’s Sunni minority, pushing some to support the fighters.

The al-Qaeda-inspired militants have seized large chunks of territory in recent weeks to form a renegade nation stretching across the Iraqi border into Syria. The sweeping offensive has forced tens of thousands of Iraqis — many of whom are members of religious minorities — to flee for their lives.

On Tuesday, U.S. Defense Secretary Chuck Hagel announced that an additional 130 U.S. troops had arrived in Iraq to help plan for a likely expansion of humanitarian relief operations in the north.

Although Hagel did not give details, he signaled that the Pentagon was laying the groundwork for a more ambitious rescue mission. Speaking to Marines at Camp Pendleton, Calif., Hagel said the extra troops would “take a closer look and give a more in-depth assessment” of the U.S. relief efforts that began last week.

The new deployment comes in addition to 775 troops previously authorized to go to Iraq to protect U.S. diplomatic facilities, work with Iraqi forces and conduct other missions.

The U.S. government has been conducting airstrikes against the Sunni extremists in the country’s north, where the semiautonomous Kurdish region has been pleading for support to keep Islamic State fighters from overrunning its boundaries.

The United States has also begun directly supplying the Kurds with weapons, U.S. officials said this week. Britain has agreed to transport military supplies “from other contributing states” to Kurdish forces so they can “provide effective protection” to refugees fleeing Islamic State militants, a spokesman for the British prime minister’s office said on Tuesday, speaking on the usual condition of anonymity.

There were indications that other European countries might start providing military aid to the Kurds or other Iraqi forces. On Tuesday, the German Defense Ministry said it was “examining” whether it should deliver non-lethal military equipment to Iraq’s armed forces.

The U.S. relief mission has been focused on airdrops of food, water and medical supplies to thousands of desperate members of the Yazidi faith who sought refuge on a mountain after the northwestern town of Sinjar was stormed by the extremists Aug. 3.

Secretary of State John F. Kerry, traveling through the Asia-Pacific region, said the additional U.S. troops being sent to Iraq will prepare for a possible rescue of the refugees. “We will make a very rapid and critical assessment because we understand it’s urgent to try to move those people off the mountain,” Kerry said during a stop at Honiara, Solomon Islands, early Wednesday. “I hope we can have more to report in short order.”

American troops

U.S. defense officials said the new team of American troops, mostly Marines and Special Operations forces, arrived in the city of Irbil and would work with the State Department, the U.S. Agency for International Development and representatives from other countries to broaden the relief operations.

Among other options, U.S. officials are considering whether to evacuate Yazidi refugees by organizing an airlift or by establishing a protected ground route for them to leave Mount Sinjar, near the Syrian border.

Hagel said the U.S. troops were not being sent to Iraq to fight. “This is not a combat-boots-on-the-ground operation,” he said. “We’re not going to have that kind of operation.”

The effort to aid the refugees suffered a setback Tuesday when an Iraqi army helicopter on a relief mission crashed shortly after takeoff. The pilot was killed and 20 people were injured, according to Kurdish officials in Dahuk. Among the injured was Vian Dakheel, the Yazidi member of parliament who helped draw attention to the plight of the Yazidis with a tearful videotaped plea to the world to help.

Alissa Rubin, a journalist for the New York Times, was also injured, the Times said. She suffered at least one broken wrist and an apparent concussion, the newspaper reported. The Iraqi army said in a statement that the cause of the crash was “technical.”

Kurdish officials said the flow of Yazidis arriving back in northern Iraq after a detour through Syria had begun to slow, with 9,000 crossing a bridge over the Tigris River on Tuesday. All together, nearly 100,000 have streamed down from Sinjar Mountain into Iraq over five days, since Syrian Kurdish fighters cleared a path for them into Syria and then back to Iraq, said Ahmed Shingali, a spokesman for Kurdish security forces — known as pesh merga — on the border. That number includes people who had lived in small, scattered villages in the area.

It is now thought that most of the Yazidis have escaped the mountain. But an unknown number remain trapped, including some who cannot manage the walk down the barren, rocky slopes.

Iraqi security forces

Iraq has been gripped in recent days by concerns that Maliki could exploit his influence over the armed forces — and Iraq’s militias — to foil a handover of power.

During a meeting with the country’s top security chiefs Tuesday, Maliki told security forces not to intervene in the political crisis and to protect the nation. But he continued to issue veiled threats.

He warned that Abadi’s appointment as prime minister designate, which he argues is a constitutional breach, could “open up the gates of hell.”

He said that members of the security forces had pulled back from the front lines of Iraq’s conflict zones upon hearing he would be replaced but that he had ordered them to return to the fight.

While ostensibly telling the armed forces to stay out of politics, Maliki added that he could not be held responsible for those who might wish to fight on his behalf.

But the Asaib Ahl al-Haq militia, which receives funding from Iran and was previously close to the prime minister, indicated that it is unlikely to fight for Maliki’s continued tenure.

“We are 100 percent with the National Alliance,” said Naim al-Abboudi, a spokesman for the group.

On Monday, the National Alliance, a group of Shiite parliamentarians, told Iraqi President Fouad Massoum that Abadi was its nominee for prime minister.

For Maliki’s government, some of the most crucial support comes from neighboring Iran, which sided with Abadi on Tuesday. Ali Shamkhani, the secretary of Iran’s National Security Council, congratulated Abadi, Iraq’s religious leaders and its political parties on the appointment, according to the state-run Islamic Republic News Agency.

Maliki has argued that he has the right to lead the next government, since his bloc won the most seats in parliament in national elections this spring. He has asked the Supreme Court to invalidate the appointment of Abadi. He remains caretaker prime minister while Abadi tries to assemble a new government.

Abadi has already secured 127 of the 165 votes he needs to form a government, just from Shiite politicians. Kurdish factions also have indicated their support.

Dhafer al-Ani, a spokesman for the Sunni Mutahidun party, said Abadi’s nomination “brings hope to the Iraqi people.” He said his bloc would be “happy to join the government” as long as Sunni demands are met, including the rolling back of laws seen as discriminatory. The bloc controls 28 seats.

Sly reported from Dahuk. Craig Whitlock, Karen DeYoung and Rick Noack in Washington, Anne Gearan in Sydney, Mustafa Salim in Baghdad and Ahmed Ramadan in Beirut contributed to this report.